Hostile downhole environment limited rod life
Petrogas Rima LLC operates more than 280 wells in the
Rima Field of southern Oman, using sucker rod pumps to
produce heavy oil with an average specific gravity of 21
API. The wells have high angles of inclination or complex
trajectories and are characterized by high concentrations of
H2S, CO2, and O2. Because of the challenging environment,
broken or parted sucker rods were common, amounting
to over half the total field failures recorded. The resulting
shutdowns were raising costs because of deferred
production, workovers, and rodstring replacements.
Proprietary coating addressed longevity challenges
Schlumberger proposed using its proprietary, field-proven
tungsten-alloy-coated sucker rods. Couplings and rods
feature high-bonded amorphous tungsten alloy plating
over high-strength base metal to enhance resistance
to delamination, wear, and corrosion stress cracking.
Hardness after heat treating is ≥850 on the Vickers
hardness scale. The coating improves corrosion resistance
without sacrificing yield or tensile strength.
Rod service life increased manyfold
The new rods were installed in seven wells and have
exhibited a dramatically increased run life despite highly
corrosive downhole fluids. By significantly reducing
workovers, they have enabled Petrogas to lower opex and
improve field economics.